A thermal flowmeter is used to measure a flow amount of a gas and includes a flow measurement element which measures a flow amount. Here, the flow amount of the gas is measured in such a manner that heat is transmitted between the flow measurement element and the gas which is a measurement object. The flow amount which is measured by the thermal flowmeter is widely used as an important control parameter of various devices. The thermal flowmeter has a feature that a gas flow amount, for example, a mass flow amount can be measured with relatively high accuracy compared to other flowmeters.
However, there has been a desire to further improve measurement accuracy of a gas flow amount. For example, in a vehicle equipped with an internal combustion engine, there is an extremely high demand of saving fuel or purifying an exhaust gas. In order to handle these demands, an intake air amount which is an important parameter of the internal combustion engine needs to be measured with high accuracy.
A thermal flowmeter which measures an amount of intake air led to an internal combustion engine includes a sub-passage which takes a part of the intake air amount and a flow measurement element which is disposed in the sub-passage. Here, a state of a measurement object gas flowing in the sub-passage is measured by the transmission of heat between the flow measurement element and the measurement object gas and an electric signal indicating an amount of the intake air led to the internal combustion engine is output.
For example, as a technology of such a thermal flowmeter, PTL 1 discloses an “air flow measurement device including a flow sensor, a circuit chip which has a circuit controlling an input and an output of the flow sensor and provided therein, a sensor assembly which has a terminal electrically connected to the circuit chip, and a terminal pin which is electrically connected to the terminal to be electrically connected to the outside, in which the terminal pin is provided with a bent portion having at least one bent shape connected to at least an outside.”